Basis of Classification — NEET Biology MCQs with Solutions
Free NEET Biology Basis of Classification MCQs with step-by-step solutions (156 questions). Part of Animal Kingdom. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Basis of Classification · easy · theory
Animals with a body cavity lined by mesoderm on both sides are called:
A. Pseudocoelomates
B. Acoelomates
C. Coelomates ✓ Correct
D. Diploblastic
Solution: A true coelom is lined by mesoderm; acoelomates lack it and pseudocoelomates have a mesoderm not fully lining the cavity.
Q2 — Basis of Classification · easy · theory
An animal that can be divided into two equal halves by any plane passing through the centre shows:
A. Radial symmetry ✓ Correct
B. Metamerism
C. Asymmetry
D. Bilateral symmetry
Solution: Radial symmetry (e.g. Cnidaria, echinoderm adults); bilateral means only one plane divides it into mirror halves.
Q3 — Basis of Classification · medium · theory
Cnidarians and ctenophores are said to be diploblastic, meaning their body is made of:
A. Two germ layers (ectoderm and endoderm) with mesoglea between ✓ Correct
B. One germ layer
C. No germ layers
D. Three germ layers
Solution: Diploblastic animals have ectoderm and endoderm with an undifferentiated mesoglea in between; triploblastic have a true mesoderm.
Q4 — Basis of Classification · medium · theory
The presence of a notochord at some stage is the defining feature of:
A. Arthropods
B. Chordates ✓ Correct
C. All coelomates
D. Annelids
Solution: A notochord (dorsal supporting rod) at some stage defines Chordata; non-chordates never have one.
Q5 — Basis of Classification · hard · theory
True segmentation (metamerism), where the body is serially divided both externally and internally, is FIRST clearly seen in:
A. Platyhelminthes
B. Porifera
C. Coelenterata
D. Annelida ✓ Correct
Solution: Annelids show true metameric segmentation; arthropods and chordates also show it, but it appears first in annelids.
Q6 — Basis of Classification · hard · theory
Which sequence correctly lists the grade of body organisation in increasing complexity?
A. Organ-system → organ → tissue → cellular
B. Tissue → cellular → organ-system → organ
C. Organ → tissue → cellular → organ-system
D. Cellular → tissue → organ → organ-system ✓ Correct
Solution: Porifera show cellular level; coelenterates tissue level; platyhelminths organ level; from Aschelminthes upward organ-system level.
Q7 — Basis of Classification · easy · numerical
The tendency to concentrate sensory and nervous tissue at the anterior end (cephalisation) is characteristically associated with which type of body symmetry?
A. Complete asymmetry
B. Spherical symmetry
C. Bilateral symmetry ✓ Correct
D. Radial symmetry
Solution: Cephalisation, the formation of a definite head, is linked with bilateral symmetry where the animal moves head-first, so sense organs and nerve centres get concentrated anteriorly.
Q8 — Basis of Classification · easy · numerical
Coelenterates (cnidarians) exhibit which grade of body organisation?
A. Organ-system level of organisation
B. Cellular level of organisation
C. Organ level of organisation
D. Tissue level of organisation ✓ Correct
Solution: In cnidarians the cells are arranged into definite tissues (division of labour) but they do not form organs, so they show the tissue level of organisation.
Q9 — Basis of Classification · easy · numerical
In diploblastic animals, the undifferentiated jelly-like layer lying between the ectoderm and the endoderm is called the:
A. Coelom
B. Mesoderm
C. Mesenchyme
D. Mesoglea ✓ Correct
Solution: Diploblastic animals have only two germ layers; the non-cellular gelatinous mesoglea lies between them. A true cellular mesoderm appears only in triploblastic animals.
Q10 — Basis of Classification · medium · numerical
Match the coelomic condition with the correct example — (i) Acoelomate, (ii) Pseudocoelomate, (iii) Eucoelomate — with (p) Ascaris, (q) Planaria, (r) Earthworm:
A. i-q, ii-p, iii-r ✓ Correct
B. i-r, ii-q, iii-p
C. i-p, ii-q, iii-r
D. i-q, ii-r, iii-p
Solution: Planaria (Platyhelminthes) is acoelomate, Ascaris (Aschelminthes) is pseudocoelomate, and the earthworm (Annelida) is a true coelomate, giving i-q, ii-p, iii-r.
Q11 — Basis of Classification · medium · numerical
Assertion (A): In a true coelomate the body cavity is lined by mesoderm on both sides. Reason (R): The coelom arises as a cavity within the mesoderm itself. Choose the correct option.
A. Both A and R are true but R is not the correct explanation of A
B. A is true but R is false
C. A is false but R is true
D. Both A and R are true and R is the correct explanation of A ✓ Correct
Solution: A true (eu)coelom is a cavity formed within and hence lined on both sides by mesoderm, so both statements are true and R correctly explains A.
Q12 — Basis of Classification · medium · numerical
Which one of the following statements about the basis of classification is INCORRECT?
A. All triploblastic animals possess a true coelom ✓ Correct
B. Radial symmetry is generally seen in animals with a tissue-level organisation
C. A pseudocoelom is a body cavity not lined by mesoderm on both sides
D. Metameric segmentation involves both external and internal serial repetition of body parts
Solution: Being triploblastic does not guarantee a coelom — flatworms are triploblastic yet acoelomate, and roundworms are only pseudocoelomate; hence that statement is incorrect.
Q13 — Basis of Classification · medium · numerical
Which of the following correctly represents an increasing order of complexity of the body cavity?
A. Acoelomate → pseudocoelomate → coelomate ✓ Correct
B. Acoelomate → coelomate → pseudocoelomate
C. Coelomate → pseudocoelomate → acoelomate
D. Pseudocoelomate → acoelomate → coelomate
Solution: Complexity increases from having no cavity (acoelomate) to a cavity not fully lined by mesoderm (pseudocoelomate) to a true mesoderm-lined cavity (coelomate).
Q14 — Basis of Classification · easy · numerical
In sponges the cells are arranged as loose aggregates with only some division of labour among them. This grade of body organisation is called:
A. Tissue level of organisation
B. Cellular level of organisation ✓ Correct
C. Organ-system level of organisation
D. Organ level of organisation
Solution: Sponges (Porifera) show the cellular level of organisation, the simplest grade, where cells act as a loose aggregate.
Q15 — Basis of Classification · easy · numerical
In which group have organs associated to form functional systems, each concerned with a specific physiological function (organ-system level of organisation)?
A. Platyhelminthes only
B. Sponges only
C. Coelenterates and ctenophores
D. Annelids, arthropods, molluscs, echinoderms and chordates ✓ Correct
Solution: Annelids, arthropods, molluscs, echinoderms and chordates show the organ-system level, in which organs are grouped into functional systems.
Q16 — Basis of Classification · easy · numerical
The grouping of tissues into organs, each specialised for a particular function (organ level of organisation), first appears in which phylum?
A. Coelenterata
B. Ctenophora
C. Porifera
D. Platyhelminthes ✓ Correct
Solution: Platyhelminthes are the first phylum to show the organ level of organisation, where tissues combine into organs.
Q17 — Basis of Classification · easy · numerical
Which two phyla both exhibit the tissue level of organisation?
A. Coelenterata and Ctenophora ✓ Correct
B. Porifera and Coelenterata
C. Annelida and Arthropoda
D. Platyhelminthes and Aschelminthes
Solution: Both coelenterates and ctenophores show the tissue level of organisation; sponges are cellular and higher phyla are organ or organ-system level.
Q18 — Basis of Classification · easy · numerical
An animal in which no plane passing through the centre divides the body into two equal halves is said to be asymmetrical. This condition is characteristic of:
A. Coelenterates
B. Roundworms (Aschelminthes)
C. Sponges (Porifera) ✓ Correct
D. Flatworms (Platyhelminthes)
Solution: Sponges are mostly asymmetrical, i.e., no plane through the centre yields two equal halves.
Q19 — Basis of Classification · easy · numerical
Radial symmetry, in which any plane passing through the central axis produces two identical halves, is shown by:
A. Platyhelminthes and aschelminthes
B. Coelenterates, ctenophores and adult echinoderms ✓ Correct
C. Sponges only
D. Annelids and arthropods
Solution: Coelenterates, ctenophores and adult echinoderms are radially symmetrical; annelids and arthropods are bilaterally symmetrical.
Q20 — Basis of Classification · easy · numerical
The body of annelids and arthropods can be divided into identical left and right halves in only one plane. This type of symmetry is:
A. Bilateral symmetry ✓ Correct
B. Asymmetry
C. Biradial symmetry
D. Radial symmetry
Solution: Bilateral symmetry allows division into equal left and right halves in one plane only, as in annelids and arthropods.
Q21 — Basis of Classification · easy · numerical
Coelenterates, whose body wall is built of only two embryonic layers, are described as:
A. Acoelomate triploblastic animals
B. Pseudocoelomate animals
C. Triploblastic animals
D. Diploblastic animals ✓ Correct
Solution: Coelenterates are diploblastic, having only an external ectoderm and internal endoderm with mesoglea in between.
Q22 — Basis of Classification · easy · numerical
Triploblastic organisation, with a mesoderm developing between the ectoderm and endoderm, is found in animals ranging from:
A. Porifera to coelenterates
B. Coelenterates to aschelminthes
C. Porifera to platyhelminthes
D. Platyhelminthes to chordates ✓ Correct
Solution: All animals from Platyhelminthes up to Chordata are triploblastic, possessing a third germ layer, the mesoderm.
Q23 — Basis of Classification · easy · numerical
The earthworm, in which the body cavity is lined by mesoderm, is an example of a:
A. Acoelomate animal
B. Pseudocoelomate animal
C. Coelomate animal ✓ Correct
D. Diploblastic animal
Solution: A body cavity lined by mesoderm is a true coelom, so mesoderm-lined animals such as the earthworm are coelomates.
Q24 — Basis of Classification · easy · numerical
In roundworms (aschelminthes) the mesoderm occurs as scattered pouches and the body cavity is not lined by mesoderm. Such animals are:
A. Acoelomates
B. Coelomates
C. Diploblastic animals
D. Pseudocoelomates ✓ Correct
Solution: Aschelminthes are pseudocoelomates: their body cavity is not lined by mesoderm, which lies only as scattered pouches.
Q25 — Basis of Classification · easy · numerical
Flatworms (platyhelminthes), which have no body cavity between the body wall and the gut, are:
A. Pseudocoelomates
B. Acoelomates ✓ Correct
C. Coelomates
D. Haemocoelomates
Solution: Platyhelminthes are acoelomates because a body cavity is absent between the gut wall and body wall.
Q26 — Basis of Classification · easy · numerical
In the earthworm the body is divided both externally and internally into a series of rings with serial repetition of organs. This phenomenon is called:
A. Metamorphosis
B. Cephalisation
C. Metagenesis
D. Metamerism ✓ Correct
Solution: The serial, external-and-internal segmentation seen in the earthworm is metameric segmentation, and the phenomenon is metamerism.
Q27 — Basis of Classification · easy · numerical
Animals such as sponges, cnidarians, flatworms, molluscs and echinoderms, which never develop a notochord, are collectively called:
A. Protochordates
B. Acraniates
C. Chordates
D. Non-chordates ✓ Correct
Solution: Animals from Porifera to Echinodermata do not form a notochord and are hence grouped as non-chordates.
Q28 — Basis of Classification · easy · numerical
A digestive system with a single opening that serves as both mouth and anus (an incomplete gut) is characteristic of:
A. Annelida
B. Echinodermata
C. Platyhelminthes ✓ Correct
D. Arthropoda
Solution: The gut of Platyhelminthes has a single opening acting as both mouth and anus, so it is called incomplete.
Q29 — Basis of Classification · easy · numerical
In which type of circulatory system is blood pumped out of the heart so that the cells and tissues are directly bathed in it?
A. Double type
B. Lymphatic type
C. Open type ✓ Correct
D. Closed type
Solution: In an open circulatory system the blood leaves the heart into spaces where tissues are bathed directly, as in arthropods.
Q30 — Basis of Classification · easy · numerical
A closed circulatory system, in which blood flows through a series of vessels of varying diameters such as arteries, veins and capillaries, is present in:
A. Sponges and coelenterates
B. Arthropods and molluscs
C. Flatworms and roundworms
D. Annelids and chordates ✓ Correct
Solution: Annelids and chordates possess a closed circulatory system with blood confined to vessels; arthropods have an open system.